Field
The present disclosure relates to illumination devices. More particularly, the disclosure relates to solid state light emitting devices mounted on a heat spreader in existing light fixtures.
Background
Solid state light emitting devices, such as light emitting diodes (LEDs), are attractive candidates for replacing conventional light sources such as incandescent, halogen and fluorescent lamps. LEDs have substantially higher light conversion efficiencies than incandescent and halogen lamps and longer lifetimes than all three of these types of conventional light sources. In addition, some types of LEDs now have higher conversion efficiencies than fluorescent light sources and still higher conversion efficiencies have been demonstrated in the laboratory. Finally, LEDs contain no mercury or other potentially dangerous materials, therefore, providing various safety and environmental benefits.
More recently, solid state devices have been used to replace high-intensity discharge (HID) lamps to provide high levels of light over large areas when energy efficiency and/or light intensity are required. These areas include roadways, parking lots, pathways, large public areas, and other outdoor applications. To increase the intensity of light in these applications, often more than one solid state light emitting device is arranged in a package. An example of a solid state light emitting device is a light emitting semiconductor chip comprising a p-n junction. An example of a package is a collection of light emitting devices arranged on a substrate and encapsulated in a phosphor to produce broad spectrum white light. This package is sometimes referred to as an “LED array.” A heat sink is often attached to the LED array to dissipate heat generated by the light emitting devices.
LEDs are being used to replace high intensity discharge (HID) lamps in legacy street lights. The conversion to LED-based street lights generally involves replacing the existing head portion attached to the top of the pole with a new LED-based head. Although it would be more cost effective to simply retrofit the head portion with an LED module, it is currently very difficult because the head portion needs to be modified to provide a thermal connection to the LED module to dissipate the heat generated by the LEDs.